The proposed work seeks to continue development of a novel ultrasound phased array applicator and control system which employs phase and frequency modification to electronically steer a focused ultrasonic beam in three dimensions for hyperthermia delivery. As a part of the development, work will continue on the applicator control system in terms of its specification for heating targeted volumes of tissue, the refinement of large-aperture array fabrication and construction techniques to improve reliability, ease of assembly, and reduce costs, and to provide the means of alignment necessary for clinical utility. In addition, a criteria for specifying the path and dwell time of the beam focal region to produce a uniformly heated volume will be defined, and a strategy for the placement of temperature monitoring probes to act as control points will be developed. Finally, enhanced methods for therapy planning using various imaging and temperature probes insertion and localization techniques will be investigated to provide the therapy preparation methodologies necessary for practical clinical implementation of the system.